A robot vehicle for hot-line job is a vehicle for high-place work having two-armed manipulators for operations and a third arm for suspending heavy matters to be supported on an electrical wire, on a manipulator base mounted on the end of a boom thereof, and wiring work and maintenance are carried out by operating them from an operation cabin on the ground in a robot vehicle or from an operation panel on a bucket provided at the end of the boom.
When all of actuators for driving the two-armed manipulators and third arm are constituted by hydraulic actuators, high positioning accuracy can not be achieved for the two-armed manipulators and, as a result, it becomes difficult to conduct teaching-playback and automatic operations based on a correcting function associated therewith. However, this makes it possible to reduce the size and weight of the third arm which has the function of suspending heavy matters and which is not required to be so high in positioning accuracy. Conversely, when all of the driving mechanisms for the two-armed manipulators and third arm are constituted by electrical actuators, high accuracy is achieved by the two-armed manipulators to facilitate corrective automatic operations such as approaching an object to be worked, whereas the third arm becomes large and heavyweight.
Under such circumstances, there is a need for a robot vehicle for hot-line job in which highly accurate positioning of a manipulator can be achieved to enable remote operations by an operator and corrective automatic operations such as approaching an object to be worked and which is loaded with a compact and lightweight third arm having a function of suspending heavy matters.
In a robot for working on hot lines, a robot which an operator boards on a bucket at the end of a vehicle for high-place work and he operates a manipulator therein, is called "an on-board type robot for working on hot lines". One possible pattern of the occurrence of an electric shock of an operator of a man-operated robot for working on hot lines is as shown in FIG. 7 in which an operator 56 touches a hot line 61 in a bucket 55. In this case, a voltage between the hot line 61 and the ground causes a current to flow through a path extending from the hot line 61 through the operator 56, the bucket 55, a boom portion (a third boom 54, a second boom 53 and a first boom 52), a vehicle 51 and to the ground. In FIG. 7, 57 designates an operation panel; 58 designates a manipulator mounting portion; 59 designates a first insulated arm portion; and 60 designates a second insulated arm portion.
For the safety of operators, safety standards for vehicles for high-place work are defined by Japan Vehicle Body Industries Association. It is specified by the standards that a leakage current should not exceed 0.5 mA as the insulating performance of a vehicle for high-place work. Further, it is specified that a voltage equivalent to twice a line voltage must be applied as a test voltage according to the standard because a leakage current varies depending on the applied voltage. A robot for working on hot lines according to the present invention is aimed at operations on hot lines at 23 kV. Therefore, referring to the electric shock shown in FIG. 7 at a man-operated robot for working on hot lines, the leakage current that flows through the operator must be 0.5 mA or less when a voltage of 46 kV is applied. For this purpose, as shown in FIG. 8, hitherto the insulation characteristics have been ensured by forming the end of the third boom 54 with an FRP hollow cylinder 62 which is an insulating material.
However, in order to keep the leakage current at 0.5 mA or less in rainy weather with the above-described configuration, the creepage distance of insulation must be long, and this has resulted in a need for always keeping the third boom in an extended state in which it spans 2 meters or more. Therefore, in rainy weather, the third boom 54 must be extended to a span of 2 meters or more even when the hot line to be worked is in a relatively low position. In this case, the weight of the manipulator portion can reduce the balance of the vehicle body to support the same and can cause the vehicle body to fall down, which makes an operation difficult or impossible. Even if an operation can be carried out with the third boom extended to a span of 2 meters or more, continued rain fall on the third boom reduces the property of shedding water of the surface of the third boom, i.e., water repellency, to make it impossible to keep the leakage current at 0.5 mA or less. When rain falls on the surface of the third boom with a voltage applied thereto, discharge occurs on the boom surface to deteriorate the FRP resin layer on surface of the third boom rapidly, thereby reducing water repellency rapidly. This makes it impossible to keep the leakage voltage at 0.5 mA or less.
When foreign substances such as sand stick to the third boom, the third boom is damaged in the area of a rotor which receives the third boom 54 during the extension and retraction of the boom, which results in a reduction of the water repellency of the third boom in a long term.
FIG. 8 is a sectional view of a structure of a conventional boom portion. In FIG. 8, a third boom 54 is an insulator which supports a manipulator portion and which is constituted by an FRP hollow cylinder 62. Since the FRP hollow cylinder 62 is an insulator, even if an operator 56 touches a hot line in a state as shown in FIG. 7 in sunny weather, the leakage current can be kept at 0.5 mA or less for a voltage of 46 kV at the hot line if the third boom 54 is extended to a span of 0.5 meters.
With the conventional structure shown in FIG. 8, however, a test on it resulted in a rapid increase of the leakage current from the third boom 54 when the surface of the third boom 54 was exposed to dirty water with a voltage applied the third boom 54. Therefore, the third boom 54 with such a structure has a leakage current of 0.5 mA or more in rainy weather, and an operator of the robot for working hot lines may have an electric shock when he or she touches the hot line.
In the case of a distribution line voltage in a 6 kV class, it is possible to maintain a level of insulation to withstand a breakdown voltage which is required to prevent phase shorting accidents by covering exposed metal regions of the manipulator and the actuator with an insulating protective cover. In the case of a voltage in a 22 kV class, a large insulation distance must be kept between the insulating protective cover and the metal regions to withstand a breakdown voltage, which has resulted in a problem in that no manipulator can be provided for practical use.
When an electrical actuator is used as the manipulator of a robot vehicle for hot-line job used in outage-free maintenance techniques for the maintenance of distribution of electricity, in order to prevent an accidental electrical shock to a human being, the end of the boom is constituted by an insulator; a generator for driving the manipulator and the like is mounted on a mount base; and electrical insulation is maintained between the vehicle and the mount base. Further, an insulated portion is provided on a forearm of a manipulator to prevent a ground fault caused by a manipulator and a phase shorting accident which occurs when tools mounted at the ends of two manipulators or the ends of the manipulators touch hot lines in different phases simultaneously during an operation.
Although an accidental electrical shock to a human being can be prevented by the prior art, there has been a problem in that it is not possible to prevent a phase shorting accident which occurs when the elbows of two manipulators or the elbow and the upper arm thereof or the upper arms thereof simultaneously touch hot lines in different phases as a result of malfunction of the manipulators and the booms themselves or an erroneous operation by the operator because the electrical actuators provided at the elbows and upper arms of the two manipulators are electrically connected through an robot controller.
Further, in the case of a robot vehicle for hot-line job which deals with high voltages, in order to improve safety by preventing a physical injury of an operator caused by an electric shock and damage to electronic devices caused by a short and ground fault, earthing is carried out through a grounding operation to connect the main bodies of the electronic devices and a ground wire electrically, and this results in a need for earthing at each movement to a site of operation. This operation is carried out by an operator, and only a visual determination is made on the physical state of grounding. Under such circumstances, it is desired to allow real time unattended determination of a state of electrical grounding in order to prevent an operator from failing to carry out earthing.
In addition, slide shafts which provided on a two-armed robot have moved back and forth relative to an object to be worked during an operation of each robot or have slid back and forth simultaneously at both arms in order to allow them approach the object to be worked. In the prior art, however, since the slides moves only in parallel with each other with the distance between the two robots fixed, it has been difficult work on an object interposed between the robots because of such a configuration.
When the robots are mounted at an increased interval to solve this, a problem arises in that the robots will occupy a larger space and become heavier. In order to allow the mounting interval of the robots to be decreased while they are idle and to allow the interval to be increased to put an object to be worked therebetween during an operation, another shaft must be added, and the addition of a shaft is problematic from the viewpoint of weight, space, cost etc.